Abstract
Heat shock proteins play important roles in the processing and trafficking of newly synthesized polypeptides and, because of their intrinsic ability to counteract the damage to protein structures, their expression is stimulated under various conditions that lead to the production of denatured proteins. This stimulation is exerted mainly at the level of transcription of heat shock genes and is mediated by a stress activated factor, referred to as HSF, that is kept inactive under normal conditions.Here, human HSF was purified by DNA-affinity chromatography for the first time and was shown to be a polypeptide of about 83 Kd that displayed the expected transcriptional stimulation activity.Physiological studies demonstrate that the triggering event in the stress activation of HSF is linked to the rate of protein synthesis as well as to the severity of the stress. A model and supporting evidence are presented, that a member of the HSP 70 family constitutes that link.